RESUMEN
Mutations in the Cyclin-dependent kinase-like 5 (CDKL5) gene cause severe neurodevelopmental disorders accompanied by intractable epilepsies, i.e. West syndrome or atypical Rett syndrome. Here we report generation of the Cdkl5 knockout mouse and show that CDKL5 controls postsynaptic localization of GluN2B-containing N-methyl-d-aspartate (NMDA) receptors in the hippocampus and regulates seizure susceptibility. Cdkl5 -/Y mice showed normal sensitivity to kainic acid; however, they displayed significant hyperexcitability to NMDA. In concordance with this result, electrophysiological analysis in the hippocampal CA1 region disclosed an increased ratio of NMDA/α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor-mediated excitatory postsynaptic currents (EPSCs) and a significantly larger decay time constant of NMDA receptor-mediated EPSCs (NMDA-EPSCs) as well as a stronger inhibition of the NMDA-EPSCs by the GluN2B-selective antagonist ifenprodil in Cdkl5 -/Y mice. Subcellular fractionation of the hippocampus from Cdkl5 -/Y mice revealed a significant increase of GluN2B and SAP102 in the PSD (postsynaptic density)-1T fraction, without changes in the S1 (post-nuclear) fraction or mRNA transcripts, indicating an intracellular distribution shift of these proteins to the PSD. Immunoelectron microscopic analysis of the hippocampal CA1 region further confirmed postsynaptic overaccumulation of GluN2B and SAP102 in Cdkl5 -/Y mice. Furthermore, ifenprodil abrogated the NMDA-induced hyperexcitability in Cdkl5 -/Y mice, suggesting that upregulation of GluN2B accounts for the enhanced seizure susceptibility. These data indicate that CDKL5 plays an important role in controlling postsynaptic localization of the GluN2B-SAP102 complex in the hippocampus and thereby regulates seizure susceptibility, and that aberrant NMDA receptor-mediated synaptic transmission underlies the pathological mechanisms of the CDKL5 loss-of-function.
Asunto(s)
Hipocampo/metabolismo , Densidad Postsináptica/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Convulsiones/metabolismo , Animales , Modelos Animales de Enfermedad , Susceptibilidad a Enfermedades/metabolismo , Antagonistas de Aminoácidos Excitadores/farmacología , Guanilato-Quinasas/metabolismo , Hipocampo/efectos de los fármacos , Hipocampo/patología , Ácido Kaínico , Proteínas de la Membrana/metabolismo , Ratones Endogámicos C57BL , Ratones Noqueados , N-Metilaspartato , Piperidinas/farmacología , Densidad Postsináptica/efectos de los fármacos , Densidad Postsináptica/patología , Proteínas Serina-Treonina Quinasas/genética , ARN Mensajero/metabolismo , Receptores de N-Metil-D-Aspartato/antagonistas & inhibidores , Convulsiones/patología , Técnicas de Cultivo de TejidosRESUMEN
Local anesthetics (LAs) inhibit endoplasmic reticulum-associated protein degradation, however the mechanisms remain elusive. Here, we show that the clinically used LAs pilsicainide and lidocaine bind directly to the 20S proteasome and inhibit its activity. Molecular dynamic calculation indicated that these LAs were bound to the ß5 subunit of the 20S proteasome, and not to the other active subunits, ß1 and ß2. Consistently, pilsicainide inhibited only chymotrypsin-like activity, whereas it did not inhibit the caspase-like and trypsin-like activities. In addition, we confirmed that the aromatic ring of these LAs was critical for inhibiting the proteasome. These LAs stabilized p53 and suppressed proliferation of p53-positive but not of p53-negative cancer cells.